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Type: Posts; User: dreNorteR

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  1. Replies
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    590

    So I imagine what was happening is that every...

    So I imagine what was happening is that every register access turned the motor on again, then the timer fires and turns it off. 100 Hz buzzer :)
    Maybe put the copy of the port at some fixed address...
  2. Got CF cards to work on Tidalwave palmtop

    So it turns out CompactFlash adapters (and probably other ATA-type cards) do work in type 1 PCMCIA slots. It's in the specs, but I'm probably not the only one who wasn't aware of this before seeing...
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    In this routine read_byte: ! HL = card...

    In this routine


    read_byte:
    ! HL = card offset, B = common/attribute

    lxi d, 0xc000
    dad d ! hl = absolute address

    di
  4. Replies
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    590

    Maybe you could turn off the floppy motor before...

    Maybe you could turn off the floppy motor before accessing the card? The original IBM PC couldn't have both drives active because of power issues too.
    You don't need to set 8 bit mode explicitly,...
  5. Replies
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    590

    Yes, you can access attribute space, but after...

    Yes, you can access attribute space, but after reading some of the spec I don't think it is necessary. Every card powers up in memory mode.
    The ATA registers are mapped at 0-7, with the lower and...
  6. Replies
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    590

    I assume they used a PCMCIA adapter with the case...

    I assume they used a PCMCIA adapter with the case removed, rather than directly plugging in the CF card.
    Wikipedia says that all CF cards support memory-mapped mode. It should also be possible to...
  7. I believe this is the fastest branchless way to...

    I believe this is the fastest branchless way to do it:



    ; DS:SI => foreground
    ; DS:BX => background
    ; ES:DI => output
    ; CX = length

    ; make BX relative to SI
  8. Replies
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    1,541

    The file name isn't the same format as in the...

    The file name isn't the same format as in the FCB, it needs to be null-terminated and have a dot between the name and extension. In my example I assumed that it was part of the program, if it should...
  9. Replies
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    1,541

    Why does the record size matter? If you are...

    Why does the record size matter?

    If you are porting working code from CP/M, the DOS functions should all be compatible, as long as you properly initialize the FCB to zero and don't modify any...
  10. Replies
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    1,423

    It would be too slow to be practical - the single...

    It would be too slow to be practical - the single step interrupt alone adds 50 clocks to every instruction, including every single REP iteration!

    The interrupt handler then would take something...
  11. Replies
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    1,801

    Having tested some more, it seems that all the...

    Having tested some more, it seems that all the extra registers are simply temporary values used by certain instructions. X1 must be involved in privilege checking and FPU emulation; for some reason,...
  12. Replies
    14
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    1,801

    Sorry, didn't see your post! F1 is not an...

    Sorry, didn't see your post!

    F1 is not an alias for F0, nothing will get written to memory if you use the F0 prefix. Also, whether you use the correct prefix or not, the CPU will hang and has to...
  13. Replies
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    1,801

    Yes, F1h on the 286 is a prefix, and different...

    Yes, F1h on the 286 is a prefix, and different from ICEBP which is a single byte opcode for 386+

    Its likely function is to access user memory from ICE mode, which explains how it interacts with 0F...
  14. Replies
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    1,801

    Made a few improvements, like monochrome support...

    Made a few improvements, like monochrome support and more reliable reset code. I didn't enable A20 before, since it worked for me without that, but many machines apparently require this. Also...
  15. Replies
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    1,801

    I made a program that lets you interactively...

    I made a program that lets you interactively change the registers. A "Load+Save" function sets everything up to immediately start the reset and save operation:



    ;come here by LOADALL, DX=0064,...
  16. Replies
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    1,801

    Tested the Harris chip and another AMD in the...

    Tested the Harris chip and another AMD in the same machine, they all work. There are some differences in both unitialized descriptors and the unknown registers, as seen after a clean boot:


    ...
  17. Replies
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    1,801

    N80C286-12 ET 037E6KX (M) AMD (C) INTEL 1982 ...

    N80C286-12
    ET 037E6KX
    (M) AMD
    (C) INTEL 1982

    Results:


    (clean boot, no HIMEM.SYS)
    ???? ???? ???? MSW stk? ???? ???? ???? ???? ???? ????
  18. Replies
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    1,801

    I assume it works on every 286, but not on any...

    I assume it works on every 286, but not on any later generation, since they don't have the 286 version of LOADALL. Maybe there is something similar on 386s, I don't have any to test this with.
  19. Replies
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    1,801

    I found the SAVEALL opcode

    Everyone who is interested in this sort of thing already knows about the LOADALL instruction. But what Intel didn't include in this no-longer-secret document is that there is an instruction that does...
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    1,902

    Older processors will keep interrupts and...

    Older processors will keep interrupts and single-stepping blocked for the entire sequence. If there is an entire 64K segment filled with the same instruction, the only way to regain control is a...
  21. Doublepost because edit expired: Looked at the...

    Doublepost because edit expired:

    Looked at the BIOS source code. RST 7 (38H) is used for a timer interrupt, so you get constant unexpected breakpoints. Change the vector to 6.
  22. Have you tried changing the restart vector? You...

    Have you tried changing the restart vector? You can do it with DBGINST.COM.



    You need to have JavaScript enabled to download.
  23. Replies
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    Nothing harmful on that site (except for a Google...

    Nothing harmful on that site (except for a Google advertising script :))

    Even the warning says that it is blocked due to a link leading somewhere else, maybe fdisk.com since that is completely...
  24. Replies
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    You need to use BRKEM to enter emulation mode,...

    You need to use BRKEM to enter emulation mode, because the mode flag is normally "locked". Some 8086 software (including BIOS code) modifies this bit, which would cause an unintended mode switch if...
  25. Device names seem to be handled differently...

    Device names seem to be handled differently depending on whether there is a path (including "\") after the drive letter. You can try this on the command line:

    type a:nul
    will not access drive,...
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